BACKGROUND: Today the use of natural substances plays a major role in improving the growth and immunity of aquatic organisms. OBJECTIVES: The purpose of the present study was to evaluate the effects of Iron nanoparticles with Lactobacillus casei as a probiotic on growth parameters and probiotic counts in rainbow trout intestine. METHODS: Seven hundred and twenty fish with 12±0.49 g initial weight were prepared and after acclimatized to the laboratory conditions divided randomly into six groups. First group was selected as control, other groups were fed with a commercial diet supplemented with 108 CFU/g Lactobacillus casei (group 2), 50 µg/kg Iron nanoparticles (group 3), 100 µg/kg Iron nanoparticles (group 4), 50 µg/kg Iron nanoparticles with 108 CFU/g Lactobacillus casei (group 5) and 100 µg/kg Iron nanoparticles with 108 CFU/g Lactobacillus casei (group 6), respectively. Biometry and intestine bacteriologic examination were carried out at days 0 and 60. RESULTS: Results showed that growth parameters (weight gain, body weight gain, specific growth rate, daily growth rate, and condition factor and food conversion rate) were significantly higher in group 5 compared with the other groups. Also, intestine bacterial counts increased by using Iron nanoparticles in combination with Lactobacillus casei. The fish that received 100 µg/kg Iron nanoparticles and probiotic had significantly higher bacterial counts in their intestine compared with the other groups. CONCLUSSIONS: Based on the obtained results we conclude that diet supplementation with Iron nanoparticles and Lactobacillus casei as a probiotic could significantly improve growth parameters in rainbow trout. However, these results would warrant further study on the clinical application of these agents.

BACKGROUND: Zeolites containing silver ion, in combination with synthetic fibers, show antibacterial activity. OBJECTIVES: The purpose of this study was to use silver zeolite indirectly as antimicrobial agents to control Streptococcus iniae infection which recently has caused disease in some of rainbow trout farms in Iran. METHODES: In this context polyurethane foams containing silver zeolite (10 and 20%) were used in water filtration of semi circulation culture system of rainbow trout fry. After addition of Streptococcus iniae (105 Cell/ml) to water in culture systems, the filters were evaluated for efficacy in inhibiting bacteria through measuring bacterial loading in water, monitoring disease symptom and culture of bacteria from kidney and spleen. RESULTS: The results indicated that filters containing silver compounds could significantly reduce load of bacteria from the water to 102 (p<0.05) compared to the control. Filter with 10% silver zeolite had higher efficiency among others. CONCLUSIONS: According to the results of this study, it seems that silver zeolite in combination with polyurethane foams has the sufficient potential to control bacterial infection and disease prevention in semi circulation system of Rainbow trout. Development of these filters and their application in control of aquatic animal diseases can result in reduction of using chemical drugs.